1. Technical Field
Various embodiments generally relate to an electronic device, and more particularly, to a semiconductor memory device and a method of operating the same.
2. Related Art
Semiconductor memory devices are classified into volatile memory devices and nonvolatile memory devices.
While the volatile memory devices have relatively fast read and write speeds, stored data is lost when their power supplies are interrupted. While the nonvolatile memory devices have relatively slow read and write speeds, stored data is retained even when their power supplies are interrupted. Therefore, the nonvolatile memory devices are used to retain stored data regardless of whether their power supplied has been interrupted or not. The nonvolatile memory devices may include a read only memory (ROM), a mask ROM (MROM), a programmable ROM (PROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a flash memory, a phase-change random access memory (PRAM), a magnetic RAM (MRAM), a resistive RAM (RRAM), a ferroelectric RAM (FRAM), etc. The flash memories may be classified as either a NOR type or a NAND type of flash memory.
Flash memories may include RAM and ROM. RAM provides advantages through programming and erasing data relatively easily. ROM provides an advantage by allowing stored data to be retained even though the power supply of the flash memory may be interrupted. The flash memory has been widely used as a storage medium for a portable electronic device such as a digital camera, a personal digital assistant (PDA), and an MP3 player, etc.
Recently, semiconductor memory devices having a 3-dimensional array structure have been studied to try and improve the degree of integration of the semiconductor memory devices.
The semiconductor memory device is configured to include a plurality of memory blocks including a plurality of memory cells. In the semiconductor memory device, the plurality of memory blocks are sequentially programmed when a program operation is performed. When the program operation on the plurality of memory blocks is completed, a threshold voltage of memory cells included in a first programmed memory block may be read as higher than a threshold voltage when the program operation on the corresponding memory block is completed. In cell strings included in an unselected memory block, due to a bias condition applied to an unselected memory block, an electron-hole pair (EHP) by gate-induced-drain-leakage (GIDL) current phenomenon may be generated between a bit line and a drain select transistor and between a source line and a source select line when the program operation on a subsequently selected memory block is performed. Electrons generated at this time may be discharged through the bit line or the source line. However, holes may be trapped in a channel of the cell string and thus channel potential is increased.